1. Field of the Invention
This invention pertains to a method and apparatus for attaching an unsupported zipper to aid across a film in a vertical form fill and seal (VFFS) apparatus. More particularly, the zipper is attached to the outside of the film in the filling tube area, after the fin seal has been made and in front of the cross seal, with the filling tube acting as a backup for the sealing bar. In an alternative embodiment, the unsupported zipper is attached to the inside of the film in the filling tube area, prior to the fin seal having been made. The zipper can be of either finger pressure or slider closing variety.
2. Description of the Prior Art
In the field of form fill and seal (FFS) machines, it is important that the machines operate at a high speed, while maintaining reliability in operation and a high quality product. In particular, the high speed placement of the zipper transversely across the film or web, can be a limiting factor in the operation.
U.S. Pat. No. 5,564,259 entitled "Method and Apparatus for Resealable Closure Addition to Form, Fill and Seal Bag", issued on Oct. 15, 1996 to Stolmeier discloses the securing of a zipper by adhesive or heat seal to the outside surface of film in a form fill and seal application, both longitudinally and in the transverse direction. Moreover, this reference discloses the transverse application of a zipper to the outside of a finished bag after the bag has been made on the VFFS machine. This apparatus and method of this reference do not achieve the efficiencies sought by the present invention. In U.S. Pat. No. 5,111,643 entitled "Apparatus and Fastener Supply Strip for Attaching Reclosable Fastener to Plastic Bags", issued on May 12, 1992 to Hobock, the zipper must be attached to a carrier strip. The carrier strip and zipper are drawn into the inside of he fill tube and then through a slit in the tube, to the outside of the tube where a section of the zipper is attached to the film. The zipper section is then separated from the carrier strip, which is drawn back into the tube through another slit and then out of the tube.
Representative prior art references include U.S. Pat. No. 5,557,907 entitled "Transverse Zipper System", issued on Sep. 24, 1996 to Malin et al.; U.S. Pat. No. 5,412,924 entitled "Method of Making Reclosable Plastic Bags on a Form, Fill and Seal Machine", issued on May 9, 1995 to Ausnit; U.S. Pat. No. 4,909,870 entitled "Method of and Apparatus for Attaching Continuously Running fastener Strip to Web Substrate", issued on Mar. 20, 1990 to Gould et al.; and U.S. Pat. No. 4,655,862 entitled "Method of and Means for Making Reclosable Bags and Method Therefor " issued on Apr. 7, 1987 to Christoff and Ausnit.
The sealing of a fully discontinuous zipper attached to a carrier tape is disclosed in European Patent Application Publication No. 0 528 721 A2 to Tilman, published on Aug. 9, 1991.